SSSDConfig: Update of config options
    
     - Added missing config options with a description
     - Removed not used or replaced options such as ldap_group_search_scope, ldap_group_search_filter, etc...
    
    Resolves:
    https://pagure.io/SSSD/sssd/issue/1362
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>